Adhesive material, method for peeling adhesive material, and pressure-sensitive adhesive tape

ABSTRACT

An object of the present invention is to provide an adhesive substance capable of being easily peeled off without damaging an adherend by giving stimulation thereto, a tape employing this adhesive substance, and a method for peeling off the adhesive substance. An adhesive substance, which contains a gas-generating agent for generating gas by stimulation, gas generated from said gas-generating agent being discharged to the outside of said adhesive substance so as not to foam said adhesive substance, and gas generated from said gas-generating agent peeling at least part of an adhesive surface of said adhesive substance off an adherend so as to decrease adhesive strength.

TECHNICAL FIELD

The present invention relates to an adhesive substance capable of beingeasily peeled off without damaging an adherend by giving stimulationthereto, a pressure-sensitive adhesive tape employing this adhesivesubstance, and a method for peeling off the adhesive substance.

BACKGROUND ART

Nowadays, adhesive substances have been widely used for a binder agentsuch as an adhesive, a sealing agent, a paint and a coating material, apressure-sensitive adhesive such as a pressure-sensitive adhesive tapeand a self-supporting tape, and the like.

The performances required for these adhesive substances vary with usesthereof, and some uses require that the adhesive substances exhibitadhesive property only while required, but can be easily peeled offthereafter.

For example, in the manufacturing process of IC chips, it has beenproposed that a thick-film wafer is reinforced by adhering to a supportplate to thereby advance the work efficiently, in the case where thethick-film wafer cut out of high-purity silicon single crystal ispolished to a predetermined thickness into a thin-film wafer. Then, itis required that the adhesive substances between the thick-film waferand the support plate stick them together firmly during the polishingprocess and, meanwhile, allows the obtained thin-film wafer to be peeledoff the support plate without damaging after the polishing process.

A method for peeling off the adhesive substances is, for example,thought to peel off by applying physical force; however, this method hasthe possibility of bringing serious damage in the case where an adherendis weak.

In addition, a method for peeling off the adhesive substances by using asolvent for dissolving them is conceivable; however, this method can notbe employed in the case where an adherend is deteriorated by thesolvent.

Thus, there has been a problem in that a firmer adhesive strength of theadhesive substances once used for adhering makes it more difficult topeel off without damaging an adherend.

By contrast, a pressure-sensitive adhesive containing an azide compoundis disclosed in Japanese Kokai Publication 2001-200234. An azidecompound decomposes to discharge nitrogen gas by being irradiated withultraviolet rays. Accordingly, when an adhesive surface stuck by using apressure-sensitive adhesive containing an azide compound is irradiatedwith ultraviolet rays, nitrogen gas discharged by the decomposition ofthe azide compound peels part of the adhesive surface of thepressure-sensitive adhesive off an adherend so as to decrease adhesivestrength, whereby the adherend can be easily peeled off.

Actually, however, nitrogen gas discharged by the decomposition of theazide compound accumulates as air bubbles, in the case where thepressure-sensitive adhesive firmly adheres to the adherend, so thatthere is a problem that the nitrogen gas is not sufficiently dischargedto the outside of the pressure-sensitive adhesive so as to peel off theadherend.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an adhesive substancecapable of being easily peeled off without damaging an adherend bygiving stimulation thereto, a pressure-sensitive adhesive tape employingthis adhesive substance, and a method for peeling off the adhesivesubstance.

The present invention provides an adhesive substance, which contains agas-generating agent for generating gas by stimulation, gas generatedfrom said gas-generating agent being discharged to the outside of saidadhesive substance so as not to foam said adhesive substance, and gasgenerated from said gas-generating agent peeling at least part of anadhesive surface of said adhesive substance off an adherend so as todecrease adhesive strength. The adhesive substance of the presentinvention is preferably crosslinked previously, and preferably containsa component crosslinkable by stimulation. The adhesive substance of thepresent invention contains two kinds or more of adhesive components, andat least one of the adhesive components is preferably crosslinkableresin. The gas-generating agent preferably does not exist as particles.In addition, the gas-generating agent is preferably an azo compound and,in particular, preferably an azoamide compound represented by thefollowing formula (1):

in the formula (1), R¹ and R² each represents the same or differentlower alkyl group, and R³ represents a saturated alkyl group with acarbon number of 2 or more.

With regard to the gas-generating agent of the present invention,stimulation for generating gas from the gas-generating agent preferablydiffers from stimulation for crosslinking the crosslinkable component.In addition, the adhesive substance of the present invention preferablycontains: a gas-generating agent for generating gas by stimulation vialight; and a component crosslinkable by stimulation via light, andpreferably has a no-overlapped wavelength range between a wavelengthrange of light for generating gas from said gas-generating agent and awavelength range of light for said crosslinkable component. In addition,the adhesive substance of the present invention containing agas-generating agent for generating gas by stimulation via heat; and acomponent crosslinkable by stimulation via heat, 10-hour half-lifetemperature of said gas-generating agent for generating gas bystimulation via heat is preferably higher than 10-hour half-lifetemperature of a thermal polymerization initiator in the componentcrosslinkable by stimulation via heat.

The present invention encompasses a method for peeling off the adhesivesubstance of the present invention containing a gas-generating agent anda crosslinkable component such that stimulation for generating gas fromthe gas-generating agent differs from stimulation for crosslinking thecrosslinkable component, the method comprising: starting to givestimulation for crosslinking the crosslinkable component to crosslinkthe crosslinkable component; and then, starting to giving stimulationfor generating gas from the gas-generating agent to generate gas fromthe gas-generating agent, generated gas being discharged to the outsideof the adhesive substance; and peeling at least part of the adhesivesurface off the adherend so as to decrease adhesive strength.

The present invention also encompasses a method for peeling off theadhesive substance of the present invention which contains: agas-generating agent for generating gas by stimulation via light; and acomponent crosslinkable by stimulation via light, and which has ano-overlapped wavelength range between a wavelength range of light forgenerating gas from said gas-generating agent and a wavelength range oflight for said crosslinkable component, the method comprising: startingto irradiate the adhesive substance with light not having the wavelengthof generating gas from the gas-generating agent but having thewavelength of crosslinking a crosslinkable component; starting toirradiate the adhesive substance with light not having the wavelength ofgenerating gas from the gas-generating agent but having the wavelengthof crosslinking a crosslinkable component; and then, starting toirradiate the adhesive substance with light having the wavelength ofgenerating gas from the gas-generating agent to generate gas from thegas-generating agent, generated gas being discharged to the outside ofthe adhesive substance to peel at least part of the adhesive surface offthe adherend so as to decrease adhesive strength.

The present invention also encompasses a method for peeling off theadhesive substance of the present invention which contains agas-generating agent for generating gas by stimulation via heat; and acomponent crosslinkable by stimulation via heat, 10-hour half-lifetemperature of said gas-generating agent for generating gas bystimulation via heat being higher than 10-hour half-life temperature ofa thermal polymerization initiator in said component crosslinkable bystimulation via heat, the method comprising: heating at a temperature ofsubstantially not generating gas from the gas-generating agent butcrosslinking the crosslinkable component; then, heating at a highertemperature than the above temperature to generate gas from thegas-generating agent, generated gas being discharged to the outside ofthe adhesive substance to peel at least part of the adhesive surface offthe adherend so as to decrease adhesive strength.

With regard to a method for peeling off the adhesive substance of thepresent invention, stimulation of at least two kinds or more selectedfrom the group consisting of light, heat, ultrasonic wave and impact ispreferably simultaneously given on an occasion of giving stimulation forgenerating gas from the gas-generating agent.

The present invention also encompasses a tape comprising a layercontaining the adhesive substance of the present invention formed on atleast one plane of a base material.

The present invention also encompasses a tape comprising a plurality oflayers containing an adhesive substance, a layer on at least one surfacethereof containing the adhesive substance of the present invention, anda layer adjoining the base material not containing the adhesivesubstance of the present invention.

The present invention also encompasses a tape comprising a plurality oflayers containing an adhesive substance, a layer on at least one surfacethereof containing the adhesive substance of the present invention.

The present invention also encompasses a tape comprising apressure-sensitive adhesive layer having adherence formed on part of asurface thereof, said pressure-sensitive adhesive layer containing theadhesive substance of the present invention.

With regard to a tape of the present invention, a non-through holehaving an opening to an exterior or through-hole is preferably formed ina layer containing the adhesive substance of the present invention.

DETAILED DISCLOSURE OF THE INVENTION

Hereinafter, the present invention will be described in detail.

An adhesive substance of the present invention contains a gas-generatingagent for generating gas by stimulation. Incidentally, an adhesivesubstance in the present specification denotes a substance havingadhesive property in a state of being applied to an adherend, and is notparticularly limited as long as it is a substance exhibiting theproperty of adhering to at least a surface to adhere to.

Stimulation for generating gas from the above-mentioned gas-generatingagent is not particularly limited, and examples thereof may includelight, heat, ultrasonic wave, impact and the like.

The above-mentioned gas-generating agent for generating gas bystimulation is not particularly limited, and an azo compound, an azidecompound and the like are appropriately used therefor.

Examples of the above-mentioned azo compound may include2,2′-azobis(N-cyclohexyl-2-methyl propionamide), 2,2′-azobis[N-(2-methylpropyl)-2-methyl propionamide], 2,2′-azobis(N-butyl-2-methylpropionamide), 2,2′-azobis[N-(2-methyl ethyl)-2-methyl propionamide],2,2′-azobis(N-hexyl-2-methyl propionamide),2,2′-azobis(N-propyl-2-methyl propionamide),2,2′-azobis(N-ethyl-2-methyl propionamide),2,2′-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide},2,2′-azobis{2-methyl-N-[2-(1-hydroxybutyl)]propionamide},2,2′-azobis[2-methyl-N-(2-hydroxyethyl)propionamide],2,2′-azobis[N-(2-propenyl)-2-methyl propionamide],2,2′-azobis[2-(5-methyl-2-imidazoline-2-yl)propane]dihydrochloride,2,2′-azobis[2-(2-imidazoline-2-yl)propane]dihydrochloride,2,2′-azobis[2-(2-imidazoline-2-yl)propane]disulfate dihydrolate,2,2′-azobis[2-(3,4,5,6-tetrahydropyrimidine-2-yl)propane]dihydrochloride,2,2′-azobis{2-[1-(2-hydroxyethyl)-2-imidazoline-2-yl]propane}dihydrochloride,2,2′-azobis[2-(2-imidazoline-2-yl)propane], 2,2′-azobis(2-methylpropionamidine)hydrochloride,2,2′-azobis(2-aminopropane)dihydrochloride,2,2′-azobis[N-(2-carboxyacyl)-2-methyl-propionamidine],2,2′-azobis{2-[N-(2-carboxyethyl)amidine]propane}, 2,2′-azobis(2-methylpropionamide oxime), dimethyl2,2′-azobis(2-methyl propionate),dimethyl2,2′-azobisisobutyrate, 4,4′-azobis(4-cyanocarbonic acid),4,4′-azobis(4-cyanopentanoic acid), 2,2′-azobis(2,4,4-trimethylpentane),and the like.

In particular, in view of being excellent in heat resistance andexcellent in solubility into a polymer having tackiness such as theacrylic acid alkyl ester polymer which will be described later, anazoamide compound represented by the following formula (1) ispreferable, such as 2,2′-azobis(N-cyclohexyl-2-methyl propionamide),2,2′-azobis[N-(2-methyl propyl)-2-methyl propionamide],2,2′-azobis(N-butyl-2-methyl propionamide), 2,2′-azobis[N-(2-methylethyl)-2-methyl propionamide], 2,2′-azobis(N-hexyl-2-methylpropionamide), 2,2′-azobis(N-propyl-2-methyl propionamide) and2,2′-azobis(N-ethyl-2-methyl propionamide).

In the formula (1), R¹ and R² each represents lower alkyl group, and R³represents a saturated alkyl group with a carbon number of 2 or more.Herein, R¹ and R² may be same as or different from each other.

These azo compounds generate nitrogen gas by stimulation via light, heatand the like.

Examples of the above-mentioned azide compound may include 3-azidemethyl-3-methyl oxetane, terephthalazide, para-tert-butylbenzazide; apolymer having an azide group such as a glycidyl azide polymer obtainedby the ring-opening polymerization of 3-azide methyl-3-methyl oxetane,and the like. These azide compounds decompose to generate nitrogen gasby giving stimulation via light of a specific wavelength, heat,ultrasonic wave, impact and the like.

Among these gas-generating agents, the above-mentioned azide compoundeasily decomposes to discharge nitrogen gas also by giving impact;therefore, it has a problem in that the handling thereof is difficult.In addition, the above-mentioned azide compound once starts to decomposeand causes a chain reaction to explosively discharge nitrogen gas beyondcontrol, whereby it has a problem in that an adherend is occasionallydamaged by the nitrogen gas explosively discharged. The quantity used ofthe above-mentioned azide compound is limited in view of such problems,and the limited quantity used occasionally brings an insufficienteffect.

Meanwhile, the above-mentioned azo compound, unlike the azide compound,does not generate gas by impact; therefore, the handling thereof isextremely easy. In addition, the above-mentioned azo compound does notcause a chain reaction to explosively generate gas and thereby does notdamage an adherend, and the interruption of irradiation of lightdiscontinues the generation of gas, whereby it is the advantage to becapable of controlling adhesive property for uses. Consequently, the azocompound is more preferably used as the above-mentioned gas-generatingagent.

The above-mentioned gas-generating agent preferably does not exist asparticles. Incidentally, in the present specification, the nonexistenceof the gas-generating agent as particles signifies that thegas-generating agent can not be confirmed when the adhesive substance ofthe present invention is observed by an electron microscope. When thegas-generating agent exists as particles in the adhesive substance ofthe present invention, light is scattered at an interface of theparticles in irradiating with light as stimulation for generating gas soas to decrease gas-generating efficiency and surface smoothness isdeteriorated in making the adhesive substance of the present inventioninto a state of a coating film.

In order that the above-mentioned gas-generating agent does not exist asparticles, a gas-generating agent to be dissolved in the adhesivesubstance of the present invention is typically selected; meanwhile, inthe case of selecting a gas-generating agent not to be dissolved in theadhesive substance of the present invention, the gas-generating agent isminutely dispersed into the adhesive substance of the present invention,for example, by using a disperser and a dispersant together therewith.

In addition, the gas-generating agent is preferably minute particles.Further, these minute particles are preferably made into finer minuteparticles as required, for example, by using a disperser, a kneadingdevice and the like. That is to say, when the adhesive substance of thepresent invention is observed by an electron microscope, thegas-generating agent is more preferably dispersed to a state of beingincapable of confirmation.

With regard to the adhesive substance of the present invention, gasgenerated from the above-mentioned gas-generating agent is discharged tothe outside of the adhesive substance. Thus, when an adhesive surfacestuck by using the adhesive substance of the present invention isirradiated with light, the gas generated from the gas-generating agentpeels at least part of the adhesive surface of the adhesive substanceoff an adherend so as to decrease adhesive strength, whereby theadherend can be easily peeled off. On this occasion, most of the gasgenerated from the gas-generating agent is preferably discharged to theoutside of the adhesive substance. When most of gas generated from theabove-mentioned gas-generating agent is not discharged to the outside ofthe adhesive substance, the gas generated from the gas-generating agentfoams the adhesive substance on the whole so as not to obtain thesufficient effect of decreasing adhesive strength and cause adhesivedeposit in an adherend. Unless adhesive deposit is caused in anadherend, part of the gas generated from the gas-generating agent may bedissolved into the adhesive substance or exist as air bubbles in theadhesive substance.

The adhesive substance of the present invention is preferablycrosslinked previously in order to adjust elastic modulus in a statebefore generating gas by stimulation to decrease adhesive strength. Forexample, the adhesive substance may be crosslinked to the degree ofretaining adhesive property by previously giving stimulation via lightor heat to photo-curing adhesive resin or thermosetting adhesive resinwhich will be described later, and a chemically crosslinked isocyanatecompound and the like may be compounded therewith. The previouscrosslinking increases elastic modulus of the adhesive substance of thepresent invention, whereby gas generated from the gas-generating agentstays as air bubbles in the adhesive substance with difficulty so as topromote the discharge to the outside of the adhesive substance.

The adhesive substance of the present invention preferably contains acomponent crosslinkable by stimulation. Examples of the above-mentionedcrosslinkable component by stimulation may include photo-curing adhesiveresin mainly containing an acrylic acid alkyl ester and/or methacrylicacid alkyl ester polymerizable polymer having a radical polymerizableunsaturated bond in a molecule and a radical polymerizablepolyfunctional oligomer or monomer and containing a photopolymerizationinitiator as required, and thermosetting adhesive resin mainlycontaining an acrylic acid alkyl ester and/or methacrylic acid alkylester polymerizable polymer having a radical polymerizable unsaturatedbond in a molecule and a radical polymerizable polyfunctional oligomeror monomer and containing a thermal polymerization initiator.

The above-mentioned polymerizable polymer can be obtained, for example,by previously synthesizing a (meth)acrylic polymer having a functionalgroup in a molecule (hereinafter, referred to as a functionalgroup-containing (meth)acrylic polymer) so as to be reacted with acompound having a functional group for reacting with the above-mentionedfunctional group and a radical polymerizable unsaturated bond in amolecule (hereinafter, referred to as a functional group-containingunsaturated compound).

The above-mentioned functional group-containing (meth)acrylic polymer,similar to the case of a general (meth)acrylic polymer as a polymerhaving tackiness at normal temperature, is obtained by conventionallycopolymerizing an acrylic acid alkyl ester and/or methacrylic acid alkylester as a main monomer, in which a carbon number of an alkyl group istypically in a range of 2 to 18, and a functional group-containingmonomer and additionally, as required, another monomer for modifyingcopolymerizable therewith. The weight-average molecular weight of theabove-mentioned functional group-containing (meth)acrylic polymer istypically 200,000 to 2,000,000.

Examples of the above-mentioned functional group-containing monomer mayinclude a carboxyl group-containing monomer such as acrylic acid andmethacrylic acid; a hydroxyl group-containing monomer such ashydroxyethyl acrylate and hydroxyethyl methacrylate; an epoxygroup-containing monomer such as glycidyl acrylate and glycidylmethacrylate; an isocyanate group-containing monomer such asisocyanateethyl acrylate and isocyanateethyl methacrylate; an aminogroup-containing monomer such as aminoethyl acrylate and aminoethylmethacrylate; and the like.

Examples of the above-mentioned another copolymerizable monomer formodifying may include various monomers used for a general (meth)acrylicpolymer, such as vinyl acetate, acrylonitrile and styrene.

As the above-mentioned functional group-containing unsaturated compoundusable for being reacted with the functional group-containing(meth)acrylic polymer, a compound similar to the above-mentionedfunctional group-containing monomer in accordance with a functionalgroup of the above-mentioned functional group-containing (meth)acrylicpolymer can be used. For example, in the case where a functional groupof the above-mentioned functional group-containing (meth)acrylic polymeris a carboxyl group, an epoxy group-containing monomer and an isocyanategroup-containing monomer are used; in the case where the functionalgroup is a hydroxyl group, an isocyanate group-containing monomer isused; in the case where the functional group is an epoxy group, acarboxyl group-containing monomer and an amide group-containing monomersuch as acrylamide are used; and in the case where the functional groupis an amino group, an epoxy group-containing monomer is used.

The above-mentioned polyfunctional oligomer or monomer is preferably anoligomer or monomer having a molecular weight of 10,000 or less, andmore preferably having a molecular weight of 5,000 or less and a radicalpolymerizable unsaturated bond number of 2 to 20 in a molecule so thatthe three-dimensional net working of a pressure-sensitive adhesive layeris efficiently performed by the irradiation of light. Examples of themore preferable polyfunctional oligomer or monomer may includetrimethylolpropane tri(meth)acrylate, tetramethylolmethanetetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritoltetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate,dipentaerythritol hexa(meth)acrylate, and the like. Additionally,examples thereof may include 1,4-butylene glycol di(meth)acrylate,1,6-hexanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate,commercially available oligoester (meth)acrylate, and the like. Thesepolyfunctional oligomers or monomers may be used singly or together intwo kinds or more.

An example of the above-mentioned photopolymerization initiator mayinclude an initiator activated by being irradiated with light having awavelength of 250 to 800 nm, and examples of such a photopolymerizationinitiator may include an acetophenone derivative compound such asmethoxyacetophenone; a benzoin ether compound such as benzoin propylether and benzoin isobutyl ether; a ketal derivative compound such asbenzyl dimethylketal and acetophenone diethylketal; a phosphine oxidederivative compound; a photo-radical polymerization initiator such as abis(η5-cyclopentadienyl)titanocene derivative compound, benzophenone,Michler's ketone, chlorothioxanthone, dodecylthioxanthone,dimethylthioxanthone, diethylthioxanthone, α-hydroxycyclohexyl phenylketone and 2-hydroxymethylphenylpropane. These photopolymerizationinitiators may be used singly or together in two kinds or more.

An example of the above-mentioned thermal polymerization initiator mayinclude an initiator which decomposes by heat to generate active radicalfor initiating polymerization and cure, and specific examples thereofmay include dicumyl peroxide, di-tert-butyl peroxide, tert-butylperoxybenzoale, tert-butyl hydroperoxide, benzoyl peroxide, cumenehydroperoxide, diisopropyl benzene hydroperoxide, para-menthanehydroperoxide, di-tert-butyl peroxide, and the like. In particular,cumene hydroperoxide, para-menthane hydroperoxide, di-tert-butylperoxide and the like are preferable in view of a high pyrolysistemperature. A commercially available thermal polymerization initiatoramong these is not particularly limited, as which Perbutyl D, PerbutylH, Perbutyl P, Permenta H (all of which are made by NOF CORPORATION) andthe like are preferable. These thermal polymerization initiators may beused singly or together in two kinds or more.

With regard to post-curing adhesive resin such as the above-mentionedphoto-curing adhesive resin or thermosetting adhesive resin, the totaladhesive resin is uniformly and promptly polymerized and crosslinked forintegration by stimulation via light or heat, whereby tan δ in a rubberyrange is remarkably decreased by polymerization and cure to considerablydeteriorate tack strength. Further, when stimulation via light or heatis given to the adhesive substance of the present invention containingthe above-mentioned post-curing adhesive resin, tan δ in a rubbery rangeis decreased so as to cure the total adhesive substance, whereby gasgenerated from the gas-generating agent stays as air bubbles in theadhesive substance with difficulty so as to promote the discharge to theoutside of the adhesive substance.

The above-mentioned effect can not be obtained unless crosslinking isadvanced before gas is generated from the gas-generating agent.Therefore, the above-mentioned crosslinkable component to be selected ispreferably a crosslinkable component such that crosslinking is formedbefore gas is generated from the gas-generating agent. Accordingly,stimulation for generating gas from the gas-generating agent andstimulation for crosslinking the crosslinkable component are preferablydifferent from or same as each other, even in which case crosslinkingcan be formed before by the presence of a no-overlapping range.

For example, in the case where stimulation for generating gas from agas-generating agent differs from stimulation for crosslinking acrosslinkable component, stimulation for generating gas from thegas-generating agent is given after stimulation for crosslinking thecrosslinkable component is given, whereby more effectively generated gascan be discharged to the outside of an adhesive substance.

In addition, for example, in the case where a gas-generating agent forgenerating gas by stimulation via light is used as a gas-generatingagent, and a component crosslinkable by light such as theabove-mentioned photo-curing adhesive resin is used as a componentcrosslinkable by stimulation, a wavelength range preferably exists suchthat a wavelength of light for generating gas from the above-mentionedgas-generating agent does not overlap with a wavelength of light forcrosslinking the above-mentioned crosslinkable component. Thus, anadhesive substance is irradiated with light of a wavelength forgenerating gas from the gas-generating agent after being irradiated withlight of a wavelength for crosslinking the crosslinkable component,whereby more effectively generated gas can be discharged to the outsideof the adhesive substance.

In addition, for example, in the case where a gas-generating agent forgenerating gas by stimulation via heat is used as a gas-generatingagent, and a component crosslinkable by heat such as the above-mentionedthermosetting adhesive resin is used as a component crosslinkable bystimulation, 10-hour half-life temperature of the above-mentionedgas-generating agent for generating gas by stimulation via heat ispreferably higher than 10-hour half-life temperature of a thermalpolymerization initiator in the above-mentioned crosslinkable componentby stimulation via heat. 10-hour half-life temperature of theabove-mentioned gas-generating agent for generating gas by stimulationvia heat is more preferably higher by 20° C. or more than 10-hourhalf-life temperature of a thermal polymerization initiator in theabove-mentioned crosslinkable component by stimulation via heat. Thus,heat of a temperature for crosslinking the crosslinkable component isapplied and, then, heat of a temperature for generating gas from thegas-generating agent is applied, whereby more effectively generated gascan be discharged to the outside of an adhesive substance.

The adhesive substance of the present invention preferably contains twokinds or more of adhesive components, and at least one of theabove-mentioned adhesive components is preferably the above-mentionedcrosslinking resin.

A resin component of the adhesive substance of the present invention isnot particularly limited, and thermoplastic resin is preferably selectedfor use from among the above-mentioned resins. In the case of usingthermoplastic resin as a resin component, an adhesive substance canadhere to an adherend in a state of being softened by heat, and therebyadheres closely even to an adherend having irregularities on a surfacethereof so as to obtain a powerful adhesive strength.

In the case where a gas-generating agent for generating gas bystimulation via light, such as an azide compound or an azo compound, isused as the above-mentioned gas-generating agent, preferably, theadhesive substance of the present invention further contains aphotosensitizer. The above-mentioned photosensitizer has the effect ofamplifying stimulation via light to the above-mentioned gas-generatingagent, so that less irradiation of light allows gas to be discharged. Inaddition, light in a wider wavelength range allows gas to be discharged;therefore, even if an adherend does not transmit light of a wavelengthfor generating gas from an azide compound or an azo compound such aspolyimide, the irradiation of light via the adherend allows gas to begenerated, leading to a wider selection of the adherend.

The above-mentioned photosensitizer is not particularly limited and, forexample, a thioxanthone sensitizer is preferable. In addition, athioxanthone sensitizer can be used as a photopolymerization initiator.

An example of method for producing the adhesive substance of the presentinvention may include a method for kneading a resin component and theabove-mentioned gas-generating agent. However, in the case where thegas-generating agent is an azide compound which easily decomposes todischarge nitrogen gas also by giving heat and impact, and once startsto decompose and cause a chain reaction so as to explosively dischargenitrogen gas beyond control, the gas-generating agent has thepossibility of starting to decompose by heat and impact in kneading,whereby it is difficult to produce an adhesive substance containing alarge quantity of the gas-generating agent.

In such a case, it is preferable to employ a method for producing anadhesive substance such that an adhesive substance material containingthe gas-generating agent, a polymerizable material and aphotopolymerization initiator is irradiated with ultraviolet rays orvisible light of a longer wavelength than the photosensitive wavelengthof an azide compound so as to polymerize the above-mentionedpolymerizable material by activating the above-mentionedphotopolymerization initiator. This method does not require the kneadingof the resin component and the gas-generating agent, which does not havethe possibility of starting to decompose by heat and impact. Inaddition, the production of an adhesive substance can be completed byone-time reaction without requiring the use of a solvent, whereby anadhesive substance containing a large quantity of the gas-generatingagent can be produced safely and easily.

In the above-mentioned production method, the polymerizable material isused such as to mainly contain an acrylic monomer or an acrylic oligomerand, additionally, the photopolymerization initiator is used such as tobe activated by being irradiated with ultraviolet rays or visible lightof a longer wavelength than the photosensitive wavelength of thegas-generating agent. Examples of such a photopolymerization initiatormay include an acetophenone derivative compound such asmethoxyacetophenone; a benzoin ether compound such as benzoin propylether and benzoin isobutyl ether; a ketal derivative compound such asbenzyl dimethylketal and acetophenone diethylketal; a phosphine oxidederivative compound; a photo-radical polymerization initiator such as abis(η5-cyclopentadienyl)titanocene derivative compound, benzophenone,Michler's ketone, chlorothioxanthone, dodecylthioxanthone,dimethylthioxanthone, diethylthioxanthone, α-hydroxycyclohexyl phenylketone and 2-hydroxymethylphenylpropane. These photopolymerizationinitiators may be used singly or together in two kinds or more.

In order to peel off the adhesive substance of the present inventioncontaining a gas-generating agent and a crosslinkable component suchthat stimulation for generating gas from the gas-generating agentdiffers from stimulation for crosslinking the crosslinkable component,stimulation for crosslinking the crosslinkable component is given first.Before or after the stimulation for crosslinking the crosslinkablecomponent finishes being given, stimulation for generating gas from thegas-generating agent is given, whereby more effectively generated gascan be discharged to the outside of the adhesive substance.

That is to say, the present invention encompasses a method for peelingoff the adhesive substance of the present invention containing agas-generating agent and a crosslinkable component such that stimulationfor generating gas from the gas-generating agent differs fromstimulation for crosslinking the crosslinkable component, the methodcomprising: starting to give stimulation for crosslinking thecrosslinkable component; and then, starting to giving stimulation forgenerating gas from the gas-generating agent to generate gas from thegas-generating agent, generated gas being discharged to the outside ofthe adhesive substance to peel at least part of the adhesive surface offthe adherend so as to decrease adhesive strength.

In order to peel off the adhesive substance of the present inventioncontaining a gas-generating agent for generating gas by stimulation vialight and a component crosslinkable by stimulation via light, theadhesive substance is first irradiated with light of a wavelength forcrosslinking the crosslinkable component in the case where a wavelengthrange exists such that a wavelength of light for generating gas from theabove-mentioned gas-generating agent does not overlap with a wavelengthof light for crosslinking the above-mentioned crosslinkable component.Before or after finishing being irradiated with the light of awavelength, the adhesive substance is irradiated with light of awavelength for generating gas from the gas-generating agent, wherebymore effectively generated gas can be discharged to the outside of theadhesive substance.

That is to say, the present invention also encompasses a method forpeeling off the adhesive substance of the present invention whichcontains: a gas-generating agent for generating gas by stimulation vialight; and a component crosslinkable by stimulation via light, and whichhas a no-overlapped wavelength range between a wavelength range of lightfor generating gas from said gas-generating agent and a wavelength rangeof light for said crosslinkable component, the method comprising:irradiating the adhesive substance with light not having a wavelength ofgenerating gas from the gas-generating agent but having a wavelength ofcrosslinking the crosslinkable component; starting to irradiate theadhesive substance with light not having the wavelength of generatinggas from the gas-generating agent but having the wavelength ofcrosslinking a crosslinkable component; and then, starting to irradiatethe adhesive substance with light having the wavelength of generatinggas from the gas-generating agent to generate gas from thegas-generating agent, generated gas being discharged to the outside ofthe adhesive substance to peel at least part of the adhesive surface offthe adherend so as to decrease adhesive strength.

In order to peel off the adhesive substance of the present inventioncontaining a gas-generating agent for generating gas by stimulation viaheat and a component crosslinkable by stimulation via heat, wherein10-hour half-life temperature of the above-mentioned gas-generatingagent for generating gas by stimulation via heat is higher than 10-hourhalf-life temperature of a thermal polymerization initiator in theabove-mentioned crosslinkable component by stimulation via heat, heat ofa temperature for crosslinking the crosslinkable component is appliedfirst. The above-mentioned temperature for crosslinking thecrosslinkable component is preferably higher by 10° C. or more than10-hour half-life temperature of a thermal polymerization initiator inthe crosslinkable component, and is more preferably higher by 20° C. ormore than 10-hour half-life temperature of a thermal polymerizationinitiator in the crosslinkable component. Before or after the heatfinishes being applied, heat of a temperature for generating gas fromthe gas-generating agent is applied, whereby more effectively generatedgas can be discharged to the outside of the adhesive substance.

That is to say, the present invention also encompasses a method forpeeling off the adhesive substance of the present invention containing agas-generating agent for generating gas by stimulation via heat; and acomponent crosslinkable by stimulation via heat, wherein 10-hourhalf-life temperature of said gas-generating agent for generating gas bystimulation via heat being higher than 10-hour half-life temperature ofa thermal polymerization initiator in said component crosslinkable bystimulation via heat, the method comprising: heating at a temperature ofsubstantially not generating gas from the gas-generating agent butcrosslinking the crosslinkable component; then, heating at a highertemperature than the above temperature to generate gas from thegas-generating agent, generated gas being discharged to the outside ofthe adhesive substance to peel at least part of the adhesive surface offthe adherend so as to decrease adhesive strength.

With regard to a method for peeling off the adhesive substance of thepresent invention, stimulation of at least two kinds or more selectedfrom the group consisting of light, heat, ultrasonic wave and impact ispreferably given simultaneously on the occasion of giving stimulationfor generating gas from a gas-generating agent. Thus, gas can begenerated more efficiently from a gas-generating agent.

The adhesive substance of the present invention can be used for variousadhesive products. Examples of the above-mentioned adhesive products mayinclude an adhesive, a pressure-sensitive adhesive, a paint, a coatingmaterial, a sealing agent and the like, in which the adhesive substanceof the present invention is used as binder resin. Such adhesive productscan be manufactured by using the adhesive substance of the presentinvention as binder resin and adding various publicly known additionagents in accordance with the purpose of each of the adhesive products.

The above-mentioned addition agents are not particularly limited, andexamples thereof may include a tackifier, a filler, a weatherabilityimparting agent, a viscosity modifier, a dyeing agent and the like.

The adhesive substance of the present invention is also preferable as apressure-sensitive adhesive of a pressure-sensitive adhesive tape suchas a pressure sensitive adhesive single coated tape, a pressuresensitive adhesive double coated tape and a nonsupport tape (aself-supporting tape). An adhesive substance in which thermoplasticresin is used as a resin component can adhere to an adherend in a stateof being softened by heat, and thereby adheres closely even to anadherend having irregularities on a surface thereof so as to obtain apowerful adhesive strength more preferably.

Examples of a pressure-sensitive adhesive tape in which the adhesivesubstance of the present invention is used as a pressure-sensitiveadhesive may include a packaging tape, a decorative tape, a surfaceprotection tape, a masking tape, a dicing tape, a back grind tape andthe like.

The present invention also encompasses a tape comprising a layercontaining the adhesive substance of the present invention formed on atleast one plane of a base material.

Examples of the tape of the present invention may include a pressuresensitive adhesive single coated tape comprising a layer containing theadhesive substance of the present invention formed on only one plane ofa base material, a pressure sensitive adhesive double coated tapecomprising a layer containing the adhesive substance of the presentinvention formed on both planes of a base material, a pressure sensitiveadhesive double coated tape such that only a pressure-sensitive adhesivelayer on one plane thereof is a layer containing the adhesive substanceof the present invention, and the like.

The tape of the present invention preferably comprises a plurality oflayers formed on at least one plane of a base material. In this case, itis more preferable that an outermost layer is a layer containing theadhesive substance of the present invention and a layer adjoining thebase material is a layer not containing the adhesive substance of thepresent invention. Thus, gas generated from the above-mentionedgas-generating agent is discharged only to an adhesive surface to anadherend and is not discharged to the side of the base material of thetape; therefore, the adherend can be peeled off without causing adhesivedeposit on the side of the adherend.

In addition, in the case where a layer containing the adhesive substanceof the present invention adjoins a layer not containing the adhesivesubstance of the present invention, the layer not containing theadhesive substance of the present invention preferably comprises a resincomponent of a different composition from a resin component composingthe layer containing the adhesive substance of the present invention.Thus, the gas-generating agent in the layer containing the adhesivesubstance of the present invention can be prevented from shifting toanother layer not containing the adhesive substance of the presentinvention.

The present invention also encompasses a tape comprising a plurality oflayers containing an adhesive substance, wherein a layer on at least onesurface thereof contains the adhesive substance of the presentinvention. Such a tape not having a base material is also called aself-supporting tape. A gas-generating agent exists only on a surfacepart of the plurality of layers containing an adhesive substance, andthereby air bubbles is not caused in a central part of a self-supportingtape so as to prevent the decrease of cohesive force, which tape can bepeeled off an adherend without causing adhesive deposit. In addition, inthe case where a layer on only one surface thereof contains the adhesivesubstance of the present invention, only an adherend on the surface canbe peeled off.

The present invention also encompasses a tape comprising apressure-sensitive adhesive layer having adherence formed on part of asurface thereof, wherein the above-mentioned pressure-sensitive adhesivelayer contains the adhesive substance of the present invention. With theuse of such a pressure-sensitive adhesive tape in which apressure-sensitive adhesive layer having adhesive property is partiallyformed, a surface not having tackiness touches a particularly fragilepart of an adherend, which part is easily damaged in peeling off, andthe tape adheres only to another comparatively stout part, whereby thetape can be peeled off without damaging the adherend. In addition, theformation of the pressure-sensitive adhesive layer in an optionalpattern allows adhesive strength of the tape to be freely adjusted.

A non-through hole having an opening to the exterior or a through-holeis preferably formed in a layer containing the adhesive substance of thepresent invention, which is formed in these tapes. Such a non-throughhole or a through-hole allows gas generated from a gas-generating agentto be more easily discharged to the outside of the adhesive substance.The discharge of gas is promoted only to a plane on the side of anopening, in the case where the above-mentioned non-through hole isformed, while the discharge of gas is promoted to planes on both sides,in the case where the above-mentioned through-hole is formed.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be further described hereinafter referring toexamples; however, the present invention is not limited thereto.

EXAMPLE 1

<Preparation of Adhesive Substance>

The following compounds were dissolved in ethyl acetate so as to beirradiated with ultraviolet rays for polymerization and obtain anacrylic copolymer having a weight-average molecular weight of 700,000.

3.5 parts by weight of 2-isocyanatoethyl acrylate was added to 100 partsby weight of resin solids content of the ethyl acetate solutioncontaining the obtained acrylic copolymer so as to be reacted, andfurther 20 parts by weight of pentaerythritol triacrylate, 0.5 part byweight of benzophenone and 0.3 part by weight of polyisocyanate weremixed with 100 parts by weight of resin solids content of the reactedethyl acetate solution to prepare the ethyl acetate solution of apressure-sensitive adhesive (1). butyl acrylate   79 parts by weightethyl acrylate   15 parts by weight acrylic acid   1 part by weight2-hydroxyethyl acrylate   5 parts by weight photopolymerizationinitiator  0.2 part by weight (IRGACURE 651, 50% - ethyl acetatesolution) lauryl mercaptan 0.01 part by weight

100 parts by weight of 3-azide methyl-3-methyl oxetane was mixed with100 parts by weight of resin solids content of the ethyl acetatesolution of a pressure-sensitive adhesive (1) to prepare the ethylacetate solution of a pressure-sensitive adhesive (2) containing anazide compound.

<Manufacture of Pressure-Sensitive Adhesive Tape>

The surface with corona treatment of a transparent polyethyleneterephthalate (PET) film having a thickness of 38 μm with coronatreatment on one side was coated with the ethyl acetate solution of apressure-sensitive adhesive (1) by a doctor knife so as to have a dryfilm thickness of approximately 10 μm and dry the coating solution byvolatilizing the solvent. The pressure-sensitive adhesive layer afterbeing dried exhibited tackiness in a dry state.

Meanwhile, a PET film having a thickness of 38 μm with release treatmenton surfaces was coated with the ethyl acetate solution of apressure-sensitive adhesive (2) by a bar coater so as to have athickness of 5 μm after being dried and dry the pressure-sensitiveadhesive layer by volatilizing the solvent.

The pressure-sensitive adhesive (1) layer formed on the PET film withcorona treatment on one side and the pressure-sensitive adhesive (2)layer formed on the PET film with release treatment were bonded togetherand thereafter cured at a temperature of 40° C. for 3 days to obtain apressure-sensitive adhesive tape 1.

<Sticking and Peeling of Pressure-Sensitive Adhesive Tape>

The obtained pressure-sensitive adhesive tape 1 was stuck to a quartzglass plate.

The obtained pressure-sensitive adhesive tape 1 was irradiated withultraviolet rays from the side of this quartz glass plate to thereafterobserve many parts, in which the pressure-sensitive adhesive was peeledoff the glass, on an adhesive interface via the glass. Thepressure-sensitive adhesive tape was capable of being easily peeled offthe glass plate.

EXAMPLE 2

<Preparation of Adhesive Substance>

100 parts by weight of 2,2′-azobis-(N-butyl-2-methyl propionamide) wasmixed with 100 parts by weight of resin solids content of the ethylacetate solution of a pressure-sensitive adhesive (1) manufactured inExample 1 to prepare the ethyl acetate solution of a pressure-sensitiveadhesive (3) containing an azo compound.

<Manufacture of Pressure-Sensitive Adhesive Tape>

The surface with corona treatment of a transparent polyethyleneterephthalate (PET) film having a thickness of 38 μm with coronatreatment on one side was coated with the ethyl acetate solution of apressure-sensitive adhesive (1) by a doctor knife so as to have a dryfilm thickness of approximately 10 μm and dry the coating solution byvolatilizing the solvent. The pressure-sensitive adhesive layer afterbeing dried exhibited tackiness in a dry state.

Meanwhile, a PET film having a thickness of 38 μm with release treatmenton surfaces was coated with the ethyl acetate solution of apressure-sensitive adhesive (3) by a bar coater so as to have athickness of 5 μm after being dried and dry the pressure-sensitiveadhesive layer by volatilizing the solvent.

The pressure-sensitive adhesive (1) layer formed on the PET film withcorona treatment on one side and the pressure-sensitive adhesive (3)layer formed on the PET film with release treatment were bonded togetherand thereafter cured at a temperature of 40° C. for 3 days to obtain apressure-sensitive adhesive tape 2.

<Sticking and Peeling of Pressure-Sensitive Adhesive Tape>

The obtained pressure-sensitive adhesive tape 2 was stuck to a quartzglass plate.

The obtained pressure-sensitive adhesive tape 1 was irradiated withultraviolet rays from the side of this quartz glass plate to thereafterobserve many parts, in which the pressure-sensitive adhesive was peeledoff the glass, on an adhesive interface via the glass. Thepressure-sensitive adhesive tape was capable of being easily peeled offthe glass plate.

EXAMPLE 3

<Preparation of Adhesive Substance>

The following compounds were dissolved in ethyl acetate so as to beirradiated with ultraviolet rays for polymerization and obtain anacrylic copolymer having a weight-average molecular weight of 700,000.

3.5 parts by weight of 2-isocyanatoethyl acrylate was added to 100 partsby weight of resin solids content of the ethyl acetate solutioncontaining the obtained acrylic copolymer so as to be reacted, andfurther 20 parts by weight of pentaerythritol triacrylate, 0.5 part byweight of a photopolymerization initiator (IRGACURE 819) and 0.3 part byweight of polyisocyanate were mixed with 100 parts by weight of resinsolids content of the reacted ethyl acetate solution to prepare theethyl acetate solution of a pressure-sensitive adhesive (4). butylacrylate   79 parts by weight ethyl acrylate   15 parts by weightacrylic acid   1 part by weight 2-hydroxyethyl acrylate   5 parts byweight photopolymerization initiator  0.2 part by weight (IRGACURE 651,50% - ethyl acetate solution) lauryl mercaptan 0.01 part by weight

100 parts by weight of 3-azide methyl-3-methyl oxetane was mixed with100 parts by weight of resin solids content of the ethyl acetatesolution of a pressure-sensitive adhesive (4) to prepare the ethylacetate solution of a pressure-sensitive adhesive (5) containing anazide compound.

<Manufacture of Pressure-Sensitive Adhesive Tape>

The surface with corona treatment of a transparent polyethyleneterephthalate (PET) film having a thickness of 38 μm with coronatreatment on one side was coated with the ethyl acetate solution of apressure-sensitive adhesive (4) by a doctor knife so as to have a dryfilm thickness of approximately 10 μm and dry the coating solution byvolatilizing the solvent. The pressure-sensitive adhesive layer afterbeing dried exhibited tackiness in a dry state.

Meanwhile, a PET film having a thickness of 38 μm with release treatmenton surfaces was coated with the ethyl acetate solution of apressure-sensitive adhesive (5) by a bar coater so as to have athickness of 5 μm after being dried and dry the pressure-sensitiveadhesive layer by volatilizing the solvent.

The pressure-sensitive adhesive (4) layer formed on the PET film withcorona treatment on one side and the pressure-sensitive adhesive (5)layer formed on the PET film with release treatment were bonded togetherand thereafter cured at a temperature of 40° C. for 3 days to obtain apressure-sensitive adhesive tape 3.

<Sticking and Peeling of Pressure-Sensitive Adhesive Tape>

The obtained pressure-sensitive adhesive tape 3 was stuck to a quartzglass plate.

The pressure-sensitive adhesive (4) layer and the pressure-sensitiveadhesive (5) layer were irradiated with ultraviolet rays having awavelength of 400 nm for polymerization and cure from the side of thisquartz glass plate by using a metal halogen lamp with short-wavelengthlight cut out via a filter. Subsequently, the pressure-sensitiveadhesive (4) layer and the pressure-sensitive adhesive (5) layer wereirradiated with ultraviolet rays having a wavelength of 313 nm tothereafter observe many parts, in which the pressure-sensitive adhesivewas peeled off the glass, on an adhesive interface via the glass. Thepressure-sensitive adhesive tape was capable of being easily peeled offthe glass plate.

EXAMPLE 4

<Preparation of Adhesive Substance>

100 parts by weight of 2,2′-azobis-(N-butyl-2-methyl propionamide) wasmixed with 100 parts by weight of resin solids content of the ethylacetate solution of a pressure-sensitive adhesive (4) manufactured inExample 3 to prepare the ethyl acetate solution of a pressure-sensitiveadhesive (6) containing an azo compound.

<Manufacture of Pressure-Sensitive Adhesive Tape>

The surface with corona treatment of a transparent polyethyleneterephthalate (PET) film having a thickness of 38 μm with coronatreatment on one side was coated with the ethyl acetate solution of apressure-sensitive adhesive (4) by a doctor knife so as to have a dryfilm thickness of approximately 10 μm and dry the coating solution byvolatilizing the solvent. The pressure-sensitive adhesive layer afterbeing dried exhibited tackiness in a dry state.

Meanwhile, a PET film having a thickness of 38 μm with release treatmenton surfaces was coated with the ethyl acetate solution of apressure-sensitive adhesive (6) by a bar coater so as to have athickness of 5 μm after being dried and dry the pressure-sensitiveadhesive layer by volatilizing the solvent.

The pressure-sensitive adhesive (4) layer formed on the PET film withcorona treatment on one side and the pressure-sensitive adhesive (6)layer formed on the PET film with release treatment were bonded togetherand thereafter cured at a temperature of 40° C. for 3 days to obtain apressure-sensitive adhesive tape 4.

<Sticking and Peeling of Pressure-Sensitive Adhesive Tape>

The obtained pressure-sensitive adhesive tape 4 was stuck to a quartzglass plate.

The pressure-sensitive adhesive (4) layer and the pressure-sensitiveadhesive (6) layer were irradiated with ultraviolet rays having awavelength of 400 nm for polymerization and cure from the side of thisquartz glass plate by using a metal halogen lamp with short-wavelengthlight cut out via a filter. Subsequently, the pressure-sensitiveadhesive (4) layer and the pressure-sensitive adhesive (6) layer wereirradiated with ultraviolet rays having a wavelength of 365 nm tothereafter observe many parts, in which the pressure-sensitive adhesivewas peeled off the glass, on an adhesive interface via the glass. Thepressure-sensitive adhesive tape was capable of being easily peeled offthe glass plate.

EXAMPLE 5

<Preparation of Adhesive Substance>

The following compounds were dissolved in ethyl acetate so as to beirradiated with ultraviolet rays for polymerization and obtain anacrylic copolymer having a weight-average molecular weight of 700,000.

3.5 parts by weight of 2-isocyanatoethyl acrylate was added to 100 partsby weight of resin solids content of the ethyl acetate solutioncontaining the obtained acrylic copolymer so as to be reacted, andfurther 20 parts by weight of pentaerythritol triacrylate, 0.5 part byweight of Perbutyl D (made by NOF corporation) and 0.3 part by weight ofpolyisocyanate were mixed with 100 parts by weight of resin solidscontent of the reacted ethyl acetate solution to prepare the ethylacetate solution of a pressure-sensitive adhesive (7). butyl acrylate  79 parts by weight ethyl acrylate   15 parts by weight acrylic acid  1 part by weight 2-hydroxyethyl acrylate   5 parts by weightphotopolymerization initiator  0.2 part by weight (IRGACURE 651, 50% -ethyl acetate solution) lauryl mercaptan 0.01 part by weight

100 parts by weight of glycidyl azide polymer was mixed with 100 partsby weight of resin solids content of the ethyl acetate solution of apressure-sensitive adhesive (7) to prepare the ethyl acetate solution ofa pressure-sensitive adhesive (8) containing an azide compound.

<Manufacture of Pressure-Sensitive Adhesive Tape>

The surface with corona treatment of a transparent PET film having athickness of 38 μm with corona treatment on one side was coated with theethyl acetate solution of a pressure-sensitive adhesive (7) by a doctorknife so as to have a dry film thickness of approximately 10 μm and drythe coating solution by volatilizing the solvent. The pressure-sensitiveadhesive layer after being dried exhibited tackiness in a dry state.

Meanwhile, a PET film having a thickness of 38 μm with release treatmenton surfaces was coated with the ethyl acetate solution of apressure-sensitive adhesive (8) by a bar coater so as to have athickness of 5 μm after being dried and dry the pressure-sensitiveadhesive layer by volatilizing the solvent.

The pressure-sensitive adhesive (7) layer formed on the PET film withcorona treatment on one side and the pressure-sensitive adhesive (8)layer formed on the PET film with release treatment were stuck togetherand, thereafter, cured at a temperature of 40° C. for 3 days to obtain apressure-sensitive adhesive tape 5.

<Sticking and Peeling of Pressure-Sensitive Adhesive Tape>

The obtained pressure-sensitive adhesive tape 5 was stuck to a quartzglass plate.

This quartz glass plate to which the pressure-sensitive adhesive tape 5was stuck was heated to 130° C. so as to polymerize and cure thepressure-sensitive adhesive (7) layer and the pressure-sensitiveadhesive (8) layer. Subsequently, the quartz glass plate was heated to180° C. to thereafter observe many parts, in which thepressure-sensitive adhesive was peeled off the glass, on an adhesiveinterface via the glass. The pressure-sensitive adhesive tape wascapable of being easily peeled off the glass plate.

EXAMPLE 6

<Preparation of Adhesive Substance>

100 parts by weight of 2,2′-azobis-(N-butyl-2-methyl propionamide) wasmixed with 100 parts by weight of resin solids content of the ethylacetate solution of a pressure-sensitive adhesive (7) manufacture inExample 5 to prepare the ethyl acetate solution of a pressure-sensitiveadhesive (9) containing an azo compound.

<Manufacture of Pressure-Sensitive Adhesive Tape>

The surface with corona treatment of a transparent PET film having athickness of 38 μm with corona treatment on one side was coated with theethyl acetate solution of a pressure-sensitive adhesive (7) by a doctorknife so as to have a dry film thickness of approximately 10 μm and drythe coating solution by volatilizing the solvent. The pressure-sensitiveadhesive layer after being dried exhibited tackiness in a dry state.

Meanwhile, a PET film having a thickness of 38 μm with release treatmenton surfaces was coated with the ethyl acetate solution of apressure-sensitive adhesive (9) by a bar coater so as to have athickness of 5 μm after being dried and dry the pressure-sensitiveadhesive layer by volatilizing the solvent.

The pressure-sensitive adhesive (7) layer formed on the PET film withcorona treatment on one side and the pressure-sensitive adhesive (9)layer formed on the PET film with release treatment were stuck togetherand, thereafter, cured at a temperature of 40° C. for 3 days to obtain apressure-sensitive adhesive tape 6.

<Sticking and Peeling of Pressure-Sensitive Adhesive Tape>

The obtained pressure-sensitive adhesive tape 6 was stuck to a quartzglass plate.

This quartz glass plate to which the pressure-sensitive adhesive tape 6was stuck was heated to 130° C. so as to polymerize and cure thepressure-sensitive adhesive (7) layer and the pressure-sensitiveadhesive (9) layer. Subsequently, the quartz glass plate was heated to180° C. to thereafter observe many parts, in which thepressure-sensitive adhesive was peeled off the glass, on an adhesiveinterface via the glass. The pressure-sensitive adhesive tape wascapable of being easily peeled off the glass plate.

EXAMPLE 7

<Sticking and Peeling of Pressure-Sensitive Adhesive Tape>

The pressure-sensitive adhesive tape 5 obtained in Example 5 was stuckto a quartz glass plate.

This quartz glass plate to which the pressure-sensitive adhesive tape 5was stuck was heated to 130° C. so as to polymerize and cure thepressure-sensitive adhesive (7) layer and the pressure-sensitiveadhesive (8) layer. After being returned to room temperature, thepressure-sensitive adhesive (7) layer and the pressure-sensitiveadhesive (8) layer were irradiated with ultraviolet rays from the sideof this quartz glass plate to thereafter observe many parts, in whichthe pressure-sensitive adhesive was peeled off the glass, on an adhesiveinterface via the glass. The pressure-sensitive adhesive tape wascapable of being easily peeled off the glass plate.

EXAMPLE 8

<Sticking and Peeling of Pressure-Sensitive Adhesive Tape>

The pressure-sensitive adhesive tape 6 obtained in Example 6 was stuckto a quartz glass plate.

This quartz glass plate to which the pressure-sensitive adhesive tape 6was stuck was heated to 130° C. so as to polymerize and cure thepressure-sensitive adhesive (7) layer and the pressure-sensitiveadhesive (9) layer. After being returned to room temperature, thepressure-sensitive adhesive (7) layer and the pressure-sensitiveadhesive (9) layer were irradiated with ultraviolet rays from the sideof this quartz glass plate to thereafter observe many parts, in whichthe pressure-sensitive adhesive was peeled off the glass, on an adhesiveinterface via the glass. The pressure-sensitive adhesive tape wascapable of being easily peeled off the glass plate.

EXAMPLE 9

<Preparation of Adhesive Substance>

The following compounds were dissolved in ethyl acetate so as to beirradiated with ultraviolet rays for polymerization and obtain anacrylic copolymer having a weight-average molecular weight of 700,000.

3.5 parts by weight of 2-isocyanatoethyl acrylate was added to 100 partsby weight of resin solids content of the ethyl acetate solutioncontaining the obtained acrylic copolymer so as to be reacted, andfurther 20 parts by weight of pentaerythritol triacrylate, 0.5 part byweight of benzophenone and 1.5 parts by weight of polyisocyanate weremixed with 100 parts by weight of resin solids content of the reactedethyl acetate solution to prepare the ethyl acetate solution of apressure-sensitive adhesive (10). butyl acrylate   79 parts by weightethyl acrylate   15 parts by weight acrylic acid   1 part by weight2-hydroxyethyl acrylate   5 parts by weight photopolymerizationinitiator  0.2 part by weight (IRGACURE 651, 50% - ethyl acetatesolution) lauryl mercaptan 0.01 part by weight

100 parts by weight of 2,2′-azobis-(N-butyl-2-methyl propionamide) wasmixed with 100 parts by weight of resin solids content of the ethylacetate solution of a pressure-sensitive adhesive (10) to prepare theethyl acetate solution of a pressure-sensitive adhesive (11) containingan azo compound.

<Manufacture of Pressure-Sensitive Adhesive Tape>

The surface with corona treatment of a transparent PET film having athickness of 38 μm with corona treatment on one side was coated with theethyl acetate solution of a pressure-sensitive adhesive (10) by a doctorknife so as to have a dry film thickness of approximately 10 μm and drythe coating solution by volatilizing the solvent. The pressure-sensitiveadhesive layer after being dried exhibited tackiness in a dry state.

Meanwhile, a PET film having a thickness of 38 μm with release treatmenton surfaces was coated with the ethyl acetate solution of apressure-sensitive adhesive (11) by a bar coater so as to have athickness of 5 μm after being dried and dry the pressure-sensitiveadhesive layer by volatilizing the solvent.

The pressure-sensitive adhesive (10) layer formed on the PET film withcorona treatment on one side and the pressure-sensitive adhesive (11)layer formed on the PET film with release treatment were stuck togetherand, thereafter, cured at a temperature of 40° C. for 3 days to obtain apressure-sensitive adhesive tape 7.

<Sticking and Peeling of Pressure-Sensitive Adhesive Tape>

The obtained pressure-sensitive adhesive tape 7 was stuck to a quartzglass plate.

The obtained pressure-sensitive adhesive tape 7 was irradiated withultraviolet rays from the side of this quartz glass plate to thereafterobserve many parts, in which the pressure-sensitive adhesive was peeledoff the glass, on an adhesive interface via the glass. Thepressure-sensitive adhesive tape was capable of being easily peeled offthe glass plate.

EXAMPLE 10

<Preparation of Adhesive Substance>

100 parts by weight of 2,2′-azobis-(N-butyl-2-methyl propionamide) wasmixed with 100 parts by weight of resin solids content of the ethylacetate solution of a pressure-sensitive adhesive (10) manufactured inExample 9 to prepare the ethyl acetate solution of a pressure-sensitiveadhesive (12) containing an azo compound.

<Manufacture of Pressure-Sensitive Adhesive Tape>

The surface with corona treatment of a transparent PET film having athickness of 38 μm with corona treatment on one side was coated with theethyl acetate solution of a pressure-sensitive adhesive (10) by a doctorknife so as to have a dry film thickness of approximately 10 μm and drythe coating solution by volatilizing the solvent. The pressure-sensitiveadhesive layer after being dried exhibited tackiness in a dry state.

Meanwhile, a PET film having a thickness of 38 μm with release treatmenton surfaces was coated with the ethyl acetate solution of apressure-sensitive adhesive (12) by a bar coater so as to have athickness of 5 μm after being dried and dry the pressure-sensitiveadhesive layer by volatilizing the solvent.

The pressure-sensitive adhesive (10) layer formed on the PET film withcorona treatment on one side and the pressure-sensitive adhesive (12)layer formed on the PET film with release treatment were stuck togetherand, thereafter, cured at a temperature of 40° C. for 3 days to obtain apressure-sensitive adhesive tape 8.

<Sticking and Peeling of Pressure-Sensitive Adhesive Tape>

The obtained pressure-sensitive adhesive tape 8 was stuck to a quartzglass plate.

The obtained pressure-sensitive adhesive tape 8 was irradiated withultraviolet rays from the side of this quartz glass plate to thereafterobserve many parts, in which the pressure-sensitive adhesive was peeledoff the glass, on an adhesive interface via the glass. Thepressure-sensitive adhesive tape was capable of being easily peeled offthe glass plate.

INDUSTRIAL APPLICABILITY

The present invention can provide an adhesive substance capable of beingeasily peeled off without damaging an adherend by giving stimulationthereto, a pressure-sensitive adhesive tape employing this adhesivesubstance, and a method for peeling off the adhesive substance.

1. An adhesive substance, which contains a gas-generating agent forgenerating gas by stimulation, gas generated from said gas-generatingagent being discharged to the outside of said adhesive substance so asnot to foam said adhesive substance, and gas generated from saidgas-generating agent peeling at least part of an adhesive surface ofsaid adhesive substance off an adherend so as to decrease adhesivestrength.
 2. The adhesive substance according to claim 1, which ispreviously crosslinked.
 3. The adhesive substance according to claim 1,which contains a component crosslinkable by stimulation.
 4. The adhesivesubstance according to claim 1, wherein the gas-generating agent doesnot exist as a particle.
 5. The adhesive substance according to claim 1,which contains two kinds or more of adhesive components, at least one ofsaid adhesive components being crosslinkable resin.
 6. The adhesivesubstance according to claim 1, wherein the gas-generating agent is anazo compound.
 7. The adhesive substance according to claim 6, whereinthe azo compound is an azoamide compound represented by the followingformula (1):

in the formula (1), R¹ and R² each represents the same or differentlower alkyl group, and R³ represents a saturated alkyl group with acarbon number of 2 or more.
 8. The adhesive substance according to claim3, wherein stimulation for generating gas from the gas-generating agentdiffers from stimulation for crosslinking the crosslinkable component.9. The adhesive substance according to claim 3, which contains: agas-generating agent for generating gas by stimulation via light; and acomponent crosslinkable by stimulation via light, and which has ano-overlapped wavelength range between a wavelength range of light forgenerating gas from said gas-generating agent and a wavelength range oflight for crosslinking said crosslinkable component.
 10. The adhesivesubstance according to claim 3, which contains a gas-generating agentfor generating gas by stimulation via heat; and a componentcrosslinkable by stimulation via heat, 10-hour half-life temperature ofsaid gas-generating agent for generating gas by stimulation via heatbeing higher than 10-hour half-life temperature of a thermalpolymerization initiator in said component crosslinkable by stimulationvia heat.
 11. The method for peeling off the adhesive substanceaccording to claim 8, which comprises: starting to give stimulation forcrosslinking the crosslinkable component; and then, starting to givingstimulation for generating gas from the gas-generating agent to generategas from the gas-generating agent, generated gas being discharged to theoutside of the adhesive substance to peel at least part of the adhesivesurface off the adherend so as to decrease adhesive strength.
 12. Themethod for peeling off the adhesive substance according to claim 9,which comprises: starting to irradiate the adhesive substance with lightnot having the wavelength of generating gas from the gas-generatingagent but having the wavelength of crosslinking a crosslinkablecomponent; and then, starting to irradiate the adhesive substance withlight having the wavelength of generating gas from the gas-generatingagent to generate gas from the gas-generating agent, generated gas beingdischarged to the outside of the adhesive substance to peel at leastpart of the adhesive surface off the adherend so as to decrease adhesivestrength.
 13. The method for peeling off the adhesive substanceaccording to claim 10, which comprises: heating at a temperature ofsubstantially not generating gas from the gas-generating agent butcrosslinking the crosslinkable component; then, heating at a highertemperature than the above temperature to generate gas from thegas-generating agent, generated gas being discharged to the outside ofthe adhesive substance to peel at least part of the adhesive surface offthe adherend so as to decrease adhesive strength.
 14. The method forpeeling off the adhesive substance according to claim 11, whereinstimulation of at least two kinds or more selected from the groupconsisting of light, heat, ultrasonic wave and impact is simultaneouslygiven on an occasion of giving stimulation for generating gas from thegas-generating agent.
 15. A tape, which comprises a layer containing theadhesive substance according to claim 1 formed on at least one plane ofa base material.
 16. A tape, which comprises a plurality of layersformed on at least one plane of a base material, an outermost layer ofsaid plurality of layers containing the adhesive substance according toclaim 1, and a layer adjoining said base material thereof not containingthe adhesive substance according to claim
 1. 17. A tape, which comprisesa plurality of layers containing an adhesive substance, a layer on atleast one surface thereof containing the adhesive substance according toclaim
 1. 18. A tape, which comprises a pressure-sensitive adhesive layerhaving adherence formed on part of a surface thereof, saidpressure-sensitive adhesive layer containing the adhesive substanceaccording to claim
 1. 19. The tape according to claim 15, wherein anon-through hole having an opening to an exterior or through-hole isformed in a layer containing the adhesive substance according to claim1.